Update Configuration_adv.h

Corrected error in AUTOTEMP instructions

Marlin/Configuration_adv.h

@@ -30,7 +30,7 @@
 
 //automatic temperature: The hot end target temperature is calculated by all the buffered lines of gcode.
 //The maximum buffered steps/sec of the extruder motor are called "se".
-//You enter the autotemp mode by a M109 S<mintemp> T<maxtemp> F<factor>
+//You enter the autotemp mode by a M109 S<mintemp> B<maxtemp> F<factor>
 // the target temperature is set to mintemp+factor*se[steps/sec] and limited by mintemp and maxtemp
 // you exit the value by any M109 without F*
 // Also, if the temperature is set to a value <mintemp, it is not changed by autotemp.